This invention relates to an apparatus for warming the washer liquid in an automobile, truck, bus, or other motor vehicle window washer system. More specifically, the invention relates to devices for warming the window washer liquid by using a heat source deriving heat from the motor vehicle engine.
Window washer liquid is used to clean dirt adhering to the front window glass of automobiles, trucks, buses, and other motor vehicles. Both chemical and physical action may be employed in the cleaning operation. For example, as a liquid solvent providing chemical action is squirted onto the front window glass, the blades of the windshield wiper simultaneously scrape the glass providing physical action.
The window washer liquid is often water alone or mixtures of water and detergent. The cleaning performance of a water-based washer liquid decreases as the liquid temperature is reduced. A higher temperature would improve the cleaning performance of the washer liquid. However, an excessively hot washer liquid would be dangerous because it may be the cause of someone being burned. The optimum range of the temperature of the window washer liquid is from 40.degree. C. to 70.degree. C.
In summer, the temperature of the washer liquid in motor vehicles is generally in the optimum range. However, in winter, the temperature of the washer liquid is generally lower than the optimum temperature range.
There are known devices which utilize automobile engine heat for warming the window washer liquid. In one type of prior art apparatus for warming up washer water, a heat exchanger is installed upon an exhaust pipe through which hot engine gases are discharged from the engine.
In the apparatus described in Japanese Utility Model Publication No. 53-34662/1978, window washer liquid is warmed by heat conducted from engine cooling water and by heat conducted by contacting the washer liquid pipe with an engine exhaust pipe.
In the apparatus described in Japanese Utility Model Publication No. 52-6978/1972, a washer liquid pipe is wound around the outer surface of the muffler for hot engine exhaust gases, and the washer liquid is heated by the heat conducted through the muffler and the pipe. This apparatus also provides withdrawal of residual liquid to a washer liquid tank.
The apparatus described in Japanese Utility Model Publication No. 52-34757/1977 employs a spirally formed copper pipe which is contacted with the outer surface of an engine exhaust pipe. Washer liquid flows through the spiral copper pipe. Efficient heat exchange occurs because the area in which the spiral copper pipe and the exhaust pipe are in contact is large.
The apparatus described in Japanese Utility Model Publication No. 53-41864/1978 has a heat exchanger with a half-cylindrical shape secured in close contact with the outer surface of an engine exhaust pipe. Also disclosed is the use of a valve arrangement to return the washer liquid heated to the boiling point back into a washer liquid holding tank.
The apparatus described in Japanese Utility Model Publication No. 53-52753/1978 makes use of a heat exchange casing made from metal mounted upon the outer surface of an engine exhaust pipe. In the heat exchange casing a fluid passage meanders. Washer liquid is heated as it flows through the fluid passage. Cooling fins are formed upon the upper surface of the heat exchange casing to prevent washer liquid from boiling.
The apparatus described in Japanese Utility Model Laying Open No. 57-151147/1982 also uses a heat exchanger which is mounted on an engine exhaust pipe in order to heat up washer liqud.
The main purpose of the apparatus in which window washer liquid is heated by heat derived from hot engine exhaust gas is to heat and melt snow, frost or ice which accumulates on the front window of the automobile. These apparatus are not designed to enhance the cleaning performance of the washer liquid.
For melting ice or snow, it is desirable that the washer liquid be very hot. Thus, in these apparatus a heat exchanger is mounted on the engine exhaust pipe, and the washer liquid is heated by the heat conducted from the hot exhaust gases. The temperature of exhaust gases is about 250.degree. C. to 300.degree. C. The outer surface of an engine exhaust pipe is as hot as the exhaust gases. At this temperature, if the washer liquid stagnates, it may be overheated to the boiling point. In order to avoid such a dangerous situation, it is necessary to constantly withdraw the heated liquid to a storage tank and re-circulate the stored liquid from the tank to the exhaust pipe. These apparatus need a complicated circulation device. In these apparatus the temperature of washer liquid reaches 80.degree. C. to 100.degree. C. This is an excessively high temperature for enhancing the cleaning performance of the window washer liquid. Such hot washer liquid also poses a danger to personnel. Furthermore, with this type of apparatus heat exchanger must be resistant to the high temperature. If the heat exchanger is a pipe wound around an exhaust pipe, the heat exchanger may be a copper pipe. If the heat exchanger is a hollow metallic plate, it may be made from aluminum or brass. Thus, the apparatus which utilize the heat contained in the hot engine exhaust gases need a metallic heat exchanger and a device for constantly circulating the washer liquid to avoid boiling.
In a second type of prior art apparatus for heating up window washer liquid, an independent washer liquid heater is employed.
The apparatus described in Japanese patent laying open No. 57-99439/1982 has an independent electric heater installed to heat washer liquid. The heater does not heat the liquid continuously. When a switch for ejecting washer liquid is actuated, the heater is switched on. This system is not subject to the danger of abrupt boiling. However, a large electric current need flow through the heater coil in order that the heater heat up the washer liquid instantly. Nevertheless, even if a relatively large current flows through the heater coil, actual heating may be insufficient because the Joule heat generated by the electric current is inefficient. Such a system wastes gasoline excessively and is therefore uneconomical.
The apparatus described in Japanese Utility Model Laying Open No. 57-151146/1982 also warms the washer liquid by an additional heater.
The main purpose of these apparatus is to melt ice or snow piled upon a front window of an automobile. This is a problem when an engine is just started after it has cooled down after being stopped for a period of time. It may be unavoidable at this time to use an additional heater because the engine is cold at starting.
Apparatus requiring an additional heater to warm the washer liquid are undesirable, uneconomical, and waste large amounts of electric power and gasoline.
Another prior art approach for cleaning front windows of automobiles involves the use of steam. With this method, water is a main component of window washer liquid. Liquid water cannot be heated above 100.degree. C. at atmospheric pressure and remain a liquid. At 100.degree. C. when washer water is further heated, it is converted to steam.
The apparatus described in Japanese Utility Model Laying Open No. 58-20953/1983 utilizes the engine cooling liquid as the washer liquid. A part of the engine cooling liquid is ejected onto the front window as steam. Vapor of the cooling water is pressurized in the cooling system. Pressurized vapor is cooled and liquefied in the radiator; then the liquefied cooling water is used to cool the engine. The cooling water cools the engine not only by the specific heat of water in the liquid state but also by the evaporation heat to convert liquid water to gaseous steam. In the cooling cycle, hot pressurized steam is generated. This apparatus ejects steam onto the front window. This apparatus requires a specific predetermined construction of the automobile. Furthermore, window washer steam is dangerous; the temperature of pressurized steam is more than 100.degree. C. The washer water need not be as hot as steam.
In another type of prior art apparatus for warming window washer liquid, the washer liquid is heated by a heat exchange with the engine cooling system liquid.
The apparatus described in Japanese Utility Model Publication No. 49-28656/1974 employs a storage tank and a second tank with an inner third tank in the circuit of the engine cooling water. Washer liquid is introduced into the inner tank and is warmed therein by cooling water in the second tank. To install this apparatus, a cooling water hose having a capacity of about one liter must be cut for connecting with the heating tank. A hose for washer liquid must also be cut to connect with the inner tank. Another problem with this apparatus is where and how the heating tank is placed in the space under the hood of the automobile. Heat exchange efficiency is good because a metallic double tank is used. However, the second tank is too expensive and too bulky. Furthermore, a large diameter pipe or hose must be used for the cooling water. Such an apparatus cannot easily be mounted under the hood in an already assembled automobile.
The apparatus described in Japanese Utility Model Publication No. 51-13295/1976 (publication date Apr. 27, 1976) warms window washer liquid and prepares warm drinking water by utilizing the heat contained in the engine cooling water. A large heat exchanger has engine cooling water flowing therethrough. Housed in the heat exchanger are two meandering pipes which carry window washer water and drinking water. While flowing through the respective two meandering pipes, washer liquid and drinking water are warmed. Because this apparatus requires the large heat exchanger to be installed in the engine cooling water system, the apparatus must be installed during original assembly of the automobile. The problems about space under the hood and about the piping must be considered at the design stage for planning the assembly of the automobile. Like other prior art, this apparatus is too bulky to be installed in an already assembled automobile. The main purpose of this apparatus is to warm water for drinking.
The apparatus described in Japanese Utility Model Laying Open No. 57-17850/1982 (date for laying open Jan. 29, 1982) has an engine cooling water pipe with an adaptor for receiving a window washer liquid tank therein. Because the outer surface of the washer liquid tank contacts the hot engine cooling water, the washer liquid in the tank is warmed. The heat exchange efficiency is good because nearly the entire tank is surrounded by the hot engine cooling water. The adaptor in the cooling water pipe must be installed during manufacturing the automobile. It is difficult to add the apparatus on an already assembled automobile. Another problem with this apparatus is the added expense resulting from the use of a double-shelled tank. Another problem is the onset of pressure loss in the cooling water.
The apparatus described in Japanese Patent Laying Open No. 58-53549/1983 (date for laying open, Aug. 30, 1983) has a large tank in the cooling system for the engine. The window washer liquid is heated by the hot cooling water in the large tank. A heat-insulating material envelops the tank to help retain heat. Because the heat-insulating material inhibits the temperature of the washer liquid in the tank from lowering, warm washer liquid can be ejected very close to the time the automobile is started. However, like the other prior art, this apparatus is also bulky and expensive. Furthermore, the large heat exchanger enveloped by the heat-insulating materials requires a large space under the hood for installation. This apparatus must be installed during manufacturing the automobile; it is very difficult to add it onto an already assembled automobile.
The apparatus described in Japanese Patent Laying Open No. 58-12854/1983 (date for laying open, Jan. 25, 1983) has a big rubber hose connecting an engine with a radiator. A spiralled copper pipe, through which the washer liquid flows, is inserted into the big rubber hose. The washer liquid is warmed in the spiralled copper pipe and returns into a tank and is accumulated therein. The purpose of the apparatus is to remove snow and ice from the front window when starting the car. The engine is cold, and the cooling water is cold at starting time. Warm washer liquid which was heated during the previous driving and was accumulated in the tank is ejected at the next starting time.
This apparatus requires a big rubber hose and a spiralled copper pipe to form a heat exchanger. The heat exchange performance is poor because the washer liquid is constantly being circulated between the tank and the heat exchanger. Furthermore, an additional pump is required for circulation of the washer liquid. Although the washer liquid in the tank is strongly heated and becomes very hot during driving, the washer liquid loses most of the heat when the engine is off. Chilled washer liquid is ejected onto the front window when starting the engine after the engine has been off for a considerable length of time. This apparatus brings about little effect on enhancement of cleaning performance of the liquid washer.
An additional problem is present and relates to an effective seal between the copper pipe and the holes of the hose through which the pipe passes. Furthermore, this apparatus requires a costly double-walled tank vessel of stainless steel, for example, to enhance the property of retaining heat in the tank.
The apparatus described in Japanese Utility Model Laying Open No. 57-5348/1982 (date for laying open, Jan. 12, 1982) has a heat exchange cylinder inserted into an engine cooling water hose which connects the engine with the radiator. A metallic spiralled pipe containing window washer liquid is inserted into the heat exchange cylinder. The heat exchange cylinder is a metallic cylinder, on both sides of which joint projections are provided. The ends of the cooling water circulating hose are attached to the joint projections. In the sidewalls an inlet hole and an outlet hole for the spiralled pipe are also provided. Ends of the washer liquid hose are affixed to the projecting ends of the spiralled pipe. The spiralled pipe is made from aluminum or copper.
This apparatus may be added onto an already assembled car. However, the heat exchange cylinder is bulky. It is difficult to install this apparatus into a narrow space under the hood. To secure the metallic heat exchange cylinder to the car body, one must perforate screw holes or must weld the cylinder to the body. It is not practical to secure the heavy cylinder by some adhesive agent. One must partly rearrange the components of the car under the hood in order to install this apparatus.
After securing the heat exchange cylinder to the car body, one must cut the cooling water hose and the window washer water hose, and one must connect the ends of the hoses with the projecting inlets and outlets of the heat exchange cylinder. Furthermore, the heat exchange cylinder itself is costly.
A review of the prior art leads to the following conclusions. Generally, the prior art apparatus have complex construction with many parts and are expensive. They cannot readily be installed in an already assembled car. They require insertion of a new heat exchanger into an engine cooling water circulating hose. The heat exchange with the window washer liquid is generally done by inserting a spiralled metal pipe into the engine cooling water.
Because the temperature of the cooling water for an engine is nearly 80.degree. C. to 90.degree. C., hot window washer liquid at about 70.degree. C. is easily obtained when the washer liquid passes through a spiralled pipe in contact with the engine cooling water. However, because the spiralled pipe is immersed in hot cooling water, the pipe must be both chemically resistant and physically resistant to heat. Therefore, the spiralled pipe must be made from copper or aluminum.
During routine operation of an automobile, window washer liquid is not used at all times. It is ejected intermittently to clean the front window glass. A quantity of washer liquid generally sufficient for cleaning a front window is about 10 cm.sup.3. Therefore, it is sufficient that merely several times 10 cm.sup.3 of washer liquid be kept warm for an ordinary use. It is unnecessary and wasteful of energy to heat the entire contents of the washer liquid tank. Moreover, the temperature of the washer liquid need not be more than 80.degree. C.
The prior art apparatus described herein are primarily aimed at removing ice, frost or snow from the front window and to do so they must eject hot washer liquid. However, for a different purpose, namely to heighten the chemical activity of the washer liquid and to enhance cleaning performance, it is not necessary to provide such hot washer liquid.
Accordingly, it is a primary object of the present invention to provide an apparatus for warming and not excessively heating window washer liquid for cleaning the front window of a motor vehicle by employing heat from the engine cooling water.
Another advantage of the present invention is that the structure is simple.
Another advantage of the present invention is that installation of the apparatus is easily accomplished.
Another advantage of the present warming apparatus is that it occupies relatively little space under the hood and is inexpensive to make and use.